Akane backed away from the door in shock and disbelief that this
could be happening in her own home.  Feeling other emotions come upon
her, she acted upon them.
______________________________________________________________________

Did Akane:
A)  Run and hide in her room?
B)  Run down the hall screaming for help?
C)  Storm into room and attack Genma?

For the short fic itself, it was a great transition for the shocking
ending...but...yes, people do use such transition for very pivotal punch
lines/events...so seeing it used not in a comedic satire, but in a sadistic,
dark, no less adult portrayal...I guess it flustered.  You see, the end had
to have...like what you asked, reason...and usually it's delicately entwined
in the long, yet inconspicuous intro...subtle hints, perhaps...indeed, if
you are continuing this leave the mystery solving to your readers by leaving
clues...

Next, for your question...I'd say Explode.  Break like a glass, shatter into
a million pieces, then recede to a miniscule recess of her mind where no
amount of therapy could take her out.